Method and apparatus for transmitting uplink control information in a wireless communication system

ABSTRACT

A method and an apparatus for transmitting uplink control information (UCI), performed by a user equipment, in a wireless communication system are provided. The method comprising: generating encoded information bits by performing channel coding on information bits of the UCI; generating a modulation symbol sequence by modulating the encoded information bits; generating a spread sequence by block-wise spreading on the modulation symbol sequences with an orthogonal sequence; and transmitting the spread sequence to a base station through an uplink control channel, wherein the information bits of the UCI comprises a first UCI bit sequence and a second UCI information bit.

TECHNICAL FIELD

The present invention relates to wireless communications, and moreparticularly, to a method and apparatus for transmitting uplink controlinformation in a wireless communication system.

BACKGROUND ART

In order to maximize efficiency of limited radio resources, an effectivetransmission and reception scheme and various methods of utilizationthereof have been proposed in a broadband wireless communication system.An orthogonal frequency division multiplexing (OFDM) system capable ofreducing inter-symbol interference (ISI) with a low complexity is takeninto consideration as one of next generation wireless communicationsystems. In the OFDM, a serially input data symbol is converted into Nparallel data symbols, and is then transmitted by being carried on eachof separated N subcarriers. The subcarriers maintain orthogonality in afrequency dimension. Each orthogonal channel experiences mutuallyindependent frequency selective fading. As a result, complexity isdecreased in a receiving end and an interval of a transmitted symbol isincreased, thereby minimizing the ISI.

In a system using the OFDM as a modulation scheme, orthogonal frequencydivision multiple access (OFDMA) is a multiple access scheme in whichmultiple access is achieved by independently providing a part ofavailable subcarrier to each user. In the OFDMA, frequency resources(i.e., subcarriers) are provided to respective users, and the respectivefrequency resources do not overlap with one another in general sincethey are independently provided to the multiple users. Consequently, thefrequency resources are allocated to the respective users in a mutuallyexclusive manner. In an OFDMA system, frequency diversity for themultiple users can be obtained by using frequency selective scheduling,and subcarriers can be allocated variously according to a permutationrule for the subcarriers. In addition, a spatial multiplexing schemeusing multiple antennas can be used to increase efficiency of a spatialdomain.

A multiple input multiple output (MIMO) technique uses multiple transmitantennas and multiple receive antennas to improve datatransmission/reception efficiency. Exemplary methods for implementingdiversity in a MIMO system include space frequency block code (SFBC),space time block code (STBC), cyclic delay diversity (CDD), frequencyswitched transmit diversity (FSTD), time switched transmit diversity(TSTD), precoding vector switching (PVS), spatial multiplexing (SM),etc. A MIMO channel matrix depending on the number of receive antennasand the number of transmit antennas can be decomposed into a pluralityof independent channels. Each independent channel is referred to as alayer or a stream. The number of layers is referred to as a rank.

Uplink control information (UCI) can be transmitted through a physicaluplink control channel (PUCCH). The UCI can include various types ofinformation such as a scheduling request (SR), anacknowledgement/non-acknowledgement (ACK/NACK) signal for hybridautomatic repeat request (HARQ), a channel quality indicator (CQI), aprecoding matrix indicator (PMI), a rank indicator (RI), etc. The PUCCHcarries various types of control information according to a format.

A carrier aggregation system has recently drawn attention. The carrieraggregation system implies a system that configures a broadband byaggregating one or more carriers having a bandwidth smaller than that ofa target broadband when the wireless communication system intends tosupport the broadband.

There is a need for a method for effectively transmitting various typesof UCI in the carrier aggregation system.

SUMMARY OF INVENTION Technical Problem

The present invention proposes a method and apparatus for transmittinguplink control information in a wireless communication system.

Technical Solution

According to an aspect of the present invention, a method fortransmitting uplink control information (UCI), performed by a userequipment, in a wireless communication system, is provided. The methodcomprising: generating encoded information bits by performing channelcoding on information bits of the UCI; generating a modulation symbolsequence by modulating the encoded information bits; generating a spreadsequence by block-wise spreading on the modulation symbol sequences withan orthogonal sequence; and transmitting the spread sequence to a basestation through an uplink control channel, wherein the information bitsof the UCI comprises a first UCI bit sequence and a second UCIinformation bit.

The spread sequence includes a sequence generated by multiplying somemodulation symbols of the modulation symbol sequence by an element ofthe orthogonal sequence.

The number of some modulation symbols may be equal to the number ofsubcarriers included in a resource block.

The transmission power of the uplink control channel may be determinedbased on the number of bits of the first UCI bit sequence and the secondUCI information bit.

The first UCI bit sequence may be an acknowledgement/non-acknowledgement(ACK/NACK) bit-stream concatenated with anacknowledgement/non-acknowledgement (ACK/NACK) information bits for eachof serving cells, and the second UCI information bit may be a schedulingrequest (SR) information bit.

The SR information bit may be appended to the end of the ACK/NACKbit-stream.

The SR information bit may be one bit.

The spread sequence can be transmitted to the base station through 1st,3rd, 4th, 5th, and 7th single carrier-frequency division multiple access(SC-FDMA) symbols in a slot consisting of 7 SC-FDMA symbols.

A reference signal may be transmitted in 2nd and 6th SC-FDMA symbols inthe slot.

The spread sequence may be transmitted via a primary cell in which theuser equipment performs an initial connection establishment procedure ora connection re-establishment procedure with respect to the basestation.

The modulation symbol sequence may be generated by performing quadraturephase shift keying (QPSK) on the encoded information bits.

According to another aspect of the present invention, an apparatus fortransmitting uplink control information is provided. The apparatuscomprising: a radio frequency (RF) unit for transmitting or receiving aradio signal; and a processor coupled to the RF unit, wherein theprocessor is configured for: generating encoded information bits byperforming channel coding on information bits of the UCI; generating amodulation symbol sequence by modulating the encoded information bits;generating a spread sequence by block-wise spreading on the modulationsymbol sequences with an orthogonal sequence; and transmitting thespread sequence to a base station through an uplink control channel,wherein the information bits of the UCI comprises a first UCI bitsequence and a second UCI information bit.

The first UCI bit sequence may be an acknowledgement/non-acknowledgement(ACK/NACK) bit-stream concatenated with anacknowledgement/non-acknowledgement (ACK/NACK) information bits for eachof serving cells, and the second UCI information bit may be a schedulingrequest (SR) information bit.

The SR information bit may be one bit, and can be appended to the end ofthe ACK/NACK bit-stream.

The transmission power of the uplink control channel may be determinedbased on the number of bits of the first UCI bit sequence and the secondUCI information bit.

Advantageous Effects

According to the present invention, various types of uplink controlinformation (UCI) can be effectively transmitted without collision whenthe UCI needs to be transmitted in the same subframe or the same slot.

DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram showing a wireless communication system.

FIG. 2 shows a radio frame structure in 3GPP LTE.

FIG. 3 shows an example of a resource grid for one DL slot.

FIG. 4 shows a structure of a DL subframe.

FIG. 5 shows a structure of a UL subframe.

FIG. 6 shows physical mapping of a PUCCH format to a control region.

FIG. 7 shows a channel structure of PUCCH formats 2/2a/2b for one slotin a normal CP.

FIG. 8 shows PUCCH formats 1a/1b for one slot in a normal CP.

FIG. 9 shows an example of constellation mapping of ACK/NACK in a normalCP.

FIG. 10 shows an example of joint coding between ACK/NACK and CQI in anextended CP.

FIG. 11 shows a method of multiplexing ACK/NACK and SR.

FIG. 12 shows constellation mapping when ACK/NACK and SR aresimultaneously transmitted.

FIG. 13 shows an example of comparing a single-carrier system and acarrier aggregation system.

FIG. 14 shows a method based on the PUCCH format 2.

FIG. 15 shows an example of the aforementioned fast codebook adaptationand slow codebook adaptation.

FIG. 16 shows an example of a method based on block spreading.

FIG. 17 shows joint coding of ACK/NACK and SR in a carrier aggregationsystem.

FIG. 18 shows a process for locating an SR information bit to an LSB andperforming channel coding in case of using slow codebook adaptation.

FIG. 19 shows an example of a process for locating an SR information bitto an MSB and performing channel coding when using slow codebookadaptation.

FIG. 20 shows an example of a process in which a UE performs jointcoding by combining different UCI and then maps it to a resource blockof each slot.

FIG. 21 shows an example of mapping spread QPSK symbols to a subcarrierin a resource block in a normal CP.

FIG. 22 is a block diagram showing a BS and a UE according to anembodiment of the present invention.

MODE FOR INVENTION

The following technologies can be used in a variety of wirelesscommunication systems, such as Code Division Multiple Access (CDMA),Frequency Division Multiple Access (FDMA), Time Division Multiple Access(TDMA), Orthogonal Frequency Division Multiple Access (OFDMA), andSingle-Carrier Frequency Division Multiple Access (SC-FDMA). The CDMAsystem can be implemented using radio technology, such as UniversalTerrestrial Radio Access (UTRA) or CDMA2000. The TDMA system can beimplemented using radio technology, such as Global System for Mobilecommunications (GSM), General Packet Radio Service (GPRS), or EnhancedData Rates for GSM Evolution (EDGE). The OFDMA system can be implementedusing radio technology, such as IEEE (Institute of Electrical andElectronics Engineers) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20,or Evolved UTRA (E-UTRA). IEEE 802.16m is the evolution of IEEE 802.16e,and it provides backward compatibility with an IEEE 802.16e-basedsystem. UTRA is part of a Universal Mobile Telecommunications System(UMTS). 3^(rd) Generation Partnership Project (3GPP) Long Term Evolution(LTE) is part of Evolved UTMS (E-UMTS) using Evolved-UMTS TerrestrialRadio Access (E-UTRA). The 3GPP LTE adopts OFDMA in the downlink andSC-FDMA in the uplink. LTE-A (Advanced) is the evolution of 3GPP LET.

In order to clarify a description, LTE-A is chiefly described, but thetechnical feature of the present invention is not limited thereto.

FIG. 1 is a diagram showing a wireless communication system.

The wireless communication system 10 includes at least one Base Station(BS) 11. The base stations 11 provide communication services torespective geographical areas (in general, called ‘cells’) 15 a, 15 b,and 15 c. The cell can be divided into a plurality of areas (called‘sectors’). A User Equipment (UE) 12 can be fixed and mobile and alsoreferred to as another terminology, such as a Mobile Station (MS), aMobile Terminal (MT), a User Terminal (UT), a Subscriber Station (SS), awireless device, a Personal Digital Assistant (PDA), a wireless modem,or a handheld device. The base station 11 commonly refers to a fixedstation which communicates with the user equipment 12, and it can alsobe referred to as another terminology, such as an evolved-NodeB (eNB), aBase Transceiver System (BTS), or an access point.

Usually, a UE may be included in one cell. The cell in which the UE isincluded is called a serving cell. The BS which provides communicationservices to the serving cell is called a serving BS. The serving BS canprovide one or more than one serving cell.

This technology can be applied to downlink or uplink. In general,downlink refers to communication from the base station 11 to the userequipment 12, and uplink refers to communication from the user equipment12 to the base station 11. A transmitter may be a part of a base station11 and a receiver may be a part of a user equipment 12 in downlink. Atransmitter may be a part of a user equipment 12 and a receiver may be apart of a base station 11 in uplink.

Layers of a radio interface protocol between the UE 12 and the BS 11 canbe classified into a first layer (L1), a second layer (L2), and a thirdlayer (L3) based on the lower three layers of the open systeminterconnection (OSI) model that is well-known in the communicationsystem.

A physical layer, i.e., the first layer, is connected to a medium accesscontrol (MAC) layer, i.e., a higher layer, through a transport channel.Data between the MAC and physical layers is transferred through thetransport channel. Further, between different physical layers, i.e.,between a physical layer of a transmitting side and a physical layer ofa receiving side, data is transferred through a physical channel.

A radio data link layer, i.e., the second layer, consists of a MAClayer, an RLC layer, and a PDCP layer. The MAC layer is a layer thatmanages mapping between a logical channel and the transport channel. TheMAC layer selects a proper transport channel to transmit data deliveredfrom the RLC layer, and adds essential control information to a headerof a MAC protocol data unit (PDU).

The RLC layer is located above the MAC layer and supports reliable datatransmission. In addition, the RLC layer segments and concatenates RLCservice data units (SDUs) delivered from an upper layer to configuredata having a suitable size for a radio section. The RLC layer of areceiver supports a reassemble function of data to restore an originalRLC SDU from the received RLC PDUs.

The PDCP layer is used only in a packet exchange area, and can performtransmission by compressing a header of an IP packet to increasetransmission efficiency of packet data in a radio channel.

The RRC layer, i.e., the third layer, exchanges radio resource controlinformation between the UE and the network in addition to controlling ofa lower layer. According to a communication state of the UE, various RRCstates (e.g., an idle mode, an RRC connected mode, etc.) are defined,and transition between the RRC states is optionally possible. In the RRClayer, various procedures related to radio resource management aredefined such as system information broadcasting, an RRC accessmanagement procedure, a multiple component carrier setup procedure, aradio bearer control procedure, a security procedure, a measurementprocedure, a mobility management procedure (handover), etc.

The wireless communication system may be any one of a multiple-inputmultiple-output (MIMO) system, a multiple-input single-output (MISO)system, a single-input single-output (SISO) system, or a single-inputmultiple-output (SIMO) system. The MIMO system uses a plurality oftransmit antennas and a plurality of receive antennas. The MISO systemuses a plurality of transmit antennas and one receive antenna. The SISOsystem uses one transmit antenna and one receive antenna. The SIMOsystem uses one transmit antenna and a plurality of receive antennas.Hereinafter, the transmit antenna denotes a physical or logical antennaused for transmission of one signal or stream. The receive antennadenotes a physical or logical antenna used for reception of one signalor stream.

FIG. 2 shows a radio frame structure in 3GPP LTE.

The section 5 of 3GPP (3rd Generation Partnership Project) TS 36.211V8.2.0 (2008-03) “Technical Specification Group Radio Access Network;Evolved Universal Terrestrial Radio Access (E-UTRA); Physical channelsand modulation (Release 8)” can be incorporated herein by reference.Referring to FIG. 2, the radio frame consists of 10 subframes. Onesubframe consists of two slots. Slots included in the radio frame arenumbered with slot numbers #0 to #19. A time required to transmit onesubframe is defined as a transmission time interval (TTI). The TTI maybe a scheduling unit for data transmission. For example, one radio framemay have a length of 10 milliseconds (ms), one subframe may have alength of 1 ms, and one slot may have a length of 0.5 ms.

One slot includes a plurality of orthogonal frequency divisionmultiplexing (OFDM) symbols in a time domain, and includes a pluralityof subcarriers in a frequency domain. Since the 3GPP LTE uses OFDMA indownlink (DL) transmission, the OFDM symbol is for representing onesymbol period, and can be referred to as other terms. For example, theOFDM symbol can also be referred to as an SC-FDMA symbol when SC-FDMA isused as an uplink (UL) multiple-access scheme. A resource block (RB) isa resource allocation unit, and includes a plurality of consecutivesubcarriers in one slot. The above radio frame is shown for exemplarypurposes only. Thus, the number of subframes included in the radio frameor the number of slots included in the subframe or the number of OFDMsymbols included in the slot may change variously.

In 3GPP LTE, it is defined such that one slot includes 7 OFDM symbols ina normal cyclic prefix (CP) and one slot includes 6 OFDM symbols in anextended CP.

A wireless communication system can be briefly classified into a systembased on a frequency division duplex (FDD) scheme and a system based ona time division duplex (TDD) scheme. In the FDD scheme, uplinktransmission and downlink transmission are achieved while occupyingdifferent frequency bands. In the TDD scheme, uplink transmission anddownlink transmission are achieved at different times while occupyingthe same frequency band. A channel response based on the TDD scheme isreciprocal in practice. This implies that a downlink channel response isalmost identical to an uplink channel response in a given frequencydomain. Therefore, in a TDD-based wireless communication system, thedownlink channel response can be advantageously obtained from the uplinkchannel response. In the TDD scheme, a full frequency band istime-divided into UL transmission and DL transmission, and thus DLtransmission performed by a BS and UL transmission performed by a UE canbe simultaneously achieved. In a TDD system in which UL transmission andDL transmission are divided on a subframe basis, UL transmission and DLtransmission are performed in different subframes.

FIG. 3 shows an example of a resource grid for one DL slot.

The DL slot includes a plurality of OFDM symbols in the time domain andan N_(RB) number of Resource Blocks (RBs) in the frequency domain. Thenumber of resource blocks N_(RB) included in a downlink slot depends ona downlink transmission bandwidth set in a cell. For example, in an LTEsystem, the number of resource blocks N_(RB) can be any one of 60 to110. One RB includes a plurality of subcarriers in frequency domain. Thestructure of a UL slot may be same as that of a DL slot.

Each element on the resource grid is referred to as a resource element(hereinafter referred to as ‘RE’). The RE on the resource grid can beidentified by an index pair (k,l) within a slot. Here, k (where k=0, . .. , N_(RB)×12−1) is a subcarrier index within the frequency domain, andl (where l=0, . . . , 6) is an OFDM symbol index within the time domain.

Here, It is illustrated that one resource block includes 7 OFDM symbolsin the time domain and 12 subcarrier in the frequency domain, resultingin 7×12 REs. However, the number of OFDM symbols and the number ofsubcarriers within a resource block are not limited thereto. The numberof OFDM symbols and the number of subcarriers can be changed in variousways according to the length of a Cyclic Prefix (CP), frequency spacing,etc. For example, in case of a normal CP, one subframe includes 7 OFDMsymbols, and in case of an extended CP, one subframe includes 6 OFDMsymbols. One OFDM symbol may use 128, 256, 512, 1024, 1536 or 2048subcarriers.

FIG. 4 shows a structure of a DL subframe.

The DL subframe includes two slots in a time domain. Each slot includes7 OFDM symbols in a normal CP. Up to three OFDM symbols (i.e., in caseof 1.4 MHz bandwidth, up to 4 OFDM symbols) located in a front portionof a first slot within the subframe correspond to a control region towhich control channels are allocated. The remaining OFDM symbolscorrespond to a data region to which a physical downlink shared channel(PDSCH) is allocated.

A physical downlink control channel (PDCCH) can carry a downlink sharedchannel (DL-SCH)'s resource allocation and transmission format, uplinkshared channel (UL-SCH)'s resource allocation information, paginginformation on a PCH, system information on a DL-SCH, a resourceallocation of a higher layer control message such as a random accessresponse transmitted through a PDSCH, a transmission power controlcommand for individual UEs included in any UE group, activation of avoice over Internet (VoIP), etc. A plurality of PDCCHs can betransmitted in the control region, and the UE can monitor the pluralityof PDCCHs. The PDCCH is transmitted on an aggregation of one or severalconsecutive control channel elements (CCEs). The CCE is a logicalallocation unit used to provide the PDCCH with a coding rate based on astate of a radio channel. The CCE corresponds to a plurality of resourceelement groups (REGs). A format of the PDCCH and the number of bits ofthe available PDCCH are determined according to a correlation betweenthe number of CCEs and the coding rate provided by the CCEs.

A BS determines a PDCCH format according to downlink control information(DCI) to be transmitted to a UE, and attaches a cyclic redundancy check(CRC) to control information. The CRC is masked with a unique identifier(referred to as a radio network temporary identifier (RNTI)) accordingto an owner or usage of the PDCCH. If the PDCCH is for a specific UE, aunique identifier (e.g., cell-RNTI (C-RNTI)) of the UE may be masked tothe CRC. Alternatively, if the PDCCH is for a paging message, a pagingindicator identifier (e.g., paging-RNTI (P-RNTI)) may be masked to theCRC. If the PDCCH is for a system information block (SIB), a systeminformation identifier and a system information RNTI (SI-RNTI) may bemasked to the CRC. To indicate a random access response that is aresponse for transmission of a random access preamble of the UE, arandom access-RNTI (RA-RNTI) may be masked to the CRC.

FIG. 5 shows a structure of a UL subframe.

The UL subframe can be divided into a control region and a data regionin frequency domain. A physical uplink control channel (PUCCH) forcarrying UL control information is allocated to the control region. Aphysical uplink shared channel (PUSCH) for carrying data is allocated tothe data region.

When it is indicated by a higher layer, a UE can support simultaneoustransmission of the PUSCH and the PUCCH.

The PUSCH is mapped to an uplink shared channel (UL-SCH) which is atransport channel. UL data transmitted on the PUSCH may be a transportblock which is a data block for the UL-SCH transmitted during TTI. Thetransport block may be user information. Alternatively, the UL data maybe multiplexed data. The multiplexed data may be attained bymultiplexing control information and the transport block for the UL-SCH.Examples of the control information multiplexed to the data include achannel quality indicator (CQI), a precoding matrix indicator (PMI), ahybrid automatic repeat request (HARQ), a rank indicator (RI), etc. TheUL data may consist of only control information.

The following description is about a PUCCH.

The PUCCH for one UE is allocated in an RB pair. RBs belonging to the RBpair occupy different subcarriers in each of a 1^(st) slot and a 2^(nd)slot. A frequency occupied by the RBs belonging to the RB pair allocatedto the PUCCH changes at a slot boundary. This is called that the RB pairallocated to the PUCCH is frequency-hopped at a slot boundary. Since theUE transmits UL control information over time through differentsubcarriers, a frequency diversity gain can be obtained. In the figure,m is a location index indicating a logical frequency-domain location ofthe RB pair allocated to the PUCCH in the subframe.

The PUCCH carries various types of control information according to aformat. A PUCCH format 1 carries a scheduling request (SR). In thiscase, an on-off keying (OOK) scheme can be used. A PUCCH format 1acarries an acknowledgement/non-acknowledgement (ACK/NACK) modulated byusing bit phase shift keying (BPSK) with respect to one codeword. APUCCH format 1b carries an ACK/NACK modulated by using quadrature phaseshift keying (QPSK) with respect to two codewords. A PUCCH format 2carries a channel quality indicator (CQI) modulated by using QPSK. PUCCHformats 2a and 2b carry CQI and ACK/NACK.

Table 1 shows a modulation scheme and the number of bits in a subframeaccording to a PUCCH format.

TABLE 1 PUCCH format Modulation scheme Number of bits per subframe,M_(bit) 1 N/A N/A 1a BPSK 1 1b QPSK 2 2 QPSK 20 2a QPSK + BPSK 21 2bQPSK + QPSK 22

Table 2 shows the number of OFDM symbols used as a PUCCH demodulationreference signal per slot.

TABLE 2 PUCCH format Normal cyclic prefix Extended cyclic prefix 1, 1a,1b 3 2 2 2 1 2a, 2b 2 N/A

Table 3 shows a position of an OFDM symbol to which a demodulationreference signal is mapped according to a PUCCH format.

TABLE 3 set of values for l PUCCH format Normal cyclic prefix Extendedcyclic prefix 1, 1a, 1b 2, 3, 4 2, 3 2, 2a, 2b 1, 5 3

FIG. 6 shows physical mapping of a PUCCH format to a control region.

Referring to FIG. 6, the PUCCH formats 2/2a/2b are mapped andtransmitted on the band-edge RBs (e.g., PUCCH region m=0, 1). A mixedPUCCH RB can be transmitted by being mapped to an adjacent RB (e.g.,m=2) towards a center of the band in an RS to which the PUCCH formats2/2a/2b are allocated. PUCCH formats 1/1a/1b by which SR and ACK/NACKare transmitted can be deployed to an RB (e.g., m=4 or m=5). The numberN⁽²⁾ _(RB) of available RBs for the PUCCH formats 2/2a/2b by which CQIis transmitted can be indicated by a UE through a broadcasting signal.

FIG. 7 shows a channel structure of PUCCH formats 2/2a/2b for one slotin a normal CP. As described above, the PUCCH formats 2/2a/2b are usedin CQI transmission.

Referring to FIG. 7, in the normal CP case, SC-FDMA symbols 1 and 5 areused for a demodulation reference symbol (DM RS) which is a UL referencesignal. In an extended CP case, an SC-FDMA symbol 3 is used for the DMRS.

10 CQI information bits are channel-coded, for example, with a codingrate of ½, thereby generating 20 coded bits. A Reed-Muller code can beused in the channel coding. After scheduling (similarly to a case wherePUSCH data is scrambled to a gold sequence having a length of 31), QPSKconstellation mapping is performed to generate QPSK modulation symbols(e.g., d₀ to d₄ in a slot 0). Each QPSK modulation symbol is modulatedby using a cyclic shift of a base RS sequence having a length of 12, andis then subjected to OFDM modulation. Then, the resultant symbol istransmitted in each of 10 SC-FDMA symbols in a subframe. 12equally-spaced cyclic shifts allow 12 different UEs to be orthogonallymultiplexed on the same PUCCH RB. A DM RS sequence applied to theSC-FDMA symbols 1 and 5 may be the base RS sequence having a length of12.

FIG. 8 shows PUCCH formats 1a/1b for one slot in a normal CP. A UL RS istransmitted in 3^(rd) to 5^(th) SC-FDMA symbols. In FIG. 8, w₀, w₁, w₂,and w₃ can be modulated in a time domain after inverse fast Fouriertransform (IFFT) modulation is performed or can be modulated in afrequency domain before IFFT modulation is performed.

In LTE, simultaneous transmission of ACK/NACK and CQI in the samesubframe can be enabled or disabled. In a case where simultaneoustransmission of the ACK/NACK and the CQI is disabled, a UE may need totransmit the ACK/NACK on a PUCCH of a subframe in which CQI feedback isconfigured. In this case, the CQI is dropped, and only the ACK/NACK istransmitted using the PUCCH formats 1a/1b.

Simultaneous transmission of the ACK/NACK and the CQI in the samesubframe can be achieved through UE-specific higher layer signaling.When simultaneous transmission is enabled, 1-bit or 2-bit ACK/NACKinformation needs to be multiplexed to the same PUCCH RB in a subframein which a BS scheduler permits simultaneous transmission of the CQI andthe ACK/NACK. In this case, it is necessary to preserve a single-carrierproperty having a low cubic metric (CM). A method of multiplexing theCQI and the ACK/NACK while preserving the single-carrier property isdifferent between a normal CP case and an extended CP case.

First, when 1-bit or 2-bit ACK/NACK and CQI are transmitted together byusing the PUCCH formats 2a/2b in the normal CP, ACK/NACK bits are notscrambled, and are subjected to BPSK (in case of 1 bit)/QPSK (in case of2 bits) modulation to generate a single HARQ ACK/NACK modulation symbold_(HARQ). The ACK is encoded as a binary ‘1’, and the NACK is encoded asa binary ‘00’. The single HARQ ACK/NACK modulation symbol d_(HARQ) isused to modulate a second RS symbol in each slot. That is, the ACK/NACKis signaled by using an RS.

FIG. 9 shows an example of constellation mapping of ACK/NACK in a normalCP.

Referring to FIG. 9, NACK (or NACK, NACK in case of transmitting two DLcodewords) is mapped to +1. Discontinuous transmission (DTX) implies acase where a UE fails to detect a DL grant in a PUCCH and where both ofACK are NACK are not necessarily transmitted, which results in a defaultNACK. The DTX is interpreted as the NACK by a BS, and triggers DLretransmission.

Next, 1- or 2-bit ACK/NACK is jointly coded with CQI in an extended CPwhich uses one RS symbol per slot.

FIG. 10 shows an example of joint coding between ACK/NACK and CQI in anextended CP.

Referring to FIG. 10, a maximum number of bits of an information bitsupported by a block code may be 13. In this case, a CQI bit K_(cqi) maybe 11 bits, and an ACK/NACK bit K_(ACK/NACK) may be 2 bits. The CQI bitand the ACK/NACK bit are jointly encoded to generate a 20-bitReed-Muller-based block code. The 20-bit codeword generated in thisprocess is transmitted through a PUCCH having the channel structuredescribed in FIG. 7 (in an extended CP case, one RS symbol is used perslot unlike in FIG. 7).

Table 4 below shows an example of a (20,A) RM code used in channelcoding of uplink control information (UCI) of 3GPP LTE. Herein, A maydenote the number of bits (i.e., K_(cqi)+K_(ACK/NACK)) of a bit-streamlinked with a CQI information bit and an ACK/NACK information bit. Ifthe bit-stream is denoted by a₀, a₁, a₂, . . . , a_(A-1), the bit-streamcan be used as an input of a channel coding block using the (20,A) RMcode.

TABLE 4 i M_(i, 0) M_(i, 1) M_(i, 2) M_(i, 3) M_(i, 4) M_(i, 5) M_(i, 6)M_(i, 7) M_(i, 8) M_(i, 9) M_(i, 10) M_(i, 11) M_(i, 12) 0 1 1 0 0 0 0 00 0 0 1 1 0 1 1 1 1 0 0 0 0 0 0 1 1 1 0 2 1 0 0 1 0 0 1 0 1 1 1 1 1 3 10 1 1 0 0 0 0 1 0 1 1 1 4 1 1 1 1 0 0 0 1 0 0 1 1 1 5 1 1 0 0 1 0 1 1 10 1 1 1 6 1 0 1 0 1 0 1 0 1 1 1 1 1 7 1 0 0 1 1 0 0 1 1 0 1 1 1 8 1 1 01 1 0 0 1 0 1 1 1 1 9 1 0 1 1 1 0 1 0 0 1 1 1 1 10 1 0 1 0 0 1 1 1 0 1 11 1 11 1 1 1 0 0 1 1 0 1 0 1 1 1 12 1 0 0 1 0 1 0 1 1 1 1 1 1 13 1 1 0 10 1 0 1 0 1 1 1 1 14 1 0 0 0 1 1 0 1 0 0 1 0 1 15 1 1 0 0 1 1 1 1 0 1 10 1 16 1 1 1 0 1 1 1 0 0 1 0 1 1 17 1 0 0 1 1 1 0 0 1 0 0 1 1 18 1 1 0 11 1 1 1 0 0 0 0 0 19 1 0 0 0 0 1 1 0 0 0 0 0 0

Channel encoding bits b₀, b₁, b₂, . . . , b_(B-1) can be generated byEquation 1 below.

$\begin{matrix}{b_{i} = {\sum\limits_{n = 0}^{A - 1}\; {( {a_{n} \cdot M_{i,n}} ){mod}\; 2}}} & \lbrack {{Equation}\mspace{14mu} 1} \rbrack\end{matrix}$

In Equation 1, i=0, 1, 2, . . . , B−1.

In LTE, ACK/NACK and SR can be multiplexed.

FIG. 11 shows a method of multiplexing ACK/NACK and SR.

Referring to FIG. 11, when ACK/NACK and SR are transmittedsimultaneously in the same subframe, a UE transmits the ACK/NACK byusing an allocated SR resource. In this case, the SR implies positiveSR. In addition, the UE may transmit ACK/NACK by using an allocatedACK/NACK resource. In this case, the SR implies negative SR. That is,according to which resource is used to transmit ACK/NACK in a subframein which the ACK/NACK and the SR are simultaneously transmitted, a BScan identify not only the ACK/NACK but also whether the SR is positiveSR or negative SR.

FIG. 12 shows constellation mapping when ACK/NACK and SR aresimultaneously transmitted.

Referring to FIG. 12, DTX/NACK and positive SR are mapped to +1 of aconstellation map, and ACK is mapped to −1.

Meanwhile, a wireless communication system can support a carrieraggregation system. The carrier aggregation system is a system thatconstitutes a broadband by aggregating one or more carriers having asmaller bandwidth than the broadband. The carrier aggregation systemimplies a system that configures a broadband by aggregating one or morecarriers having a bandwidth smaller than that of a target broadband whenthe wireless communication system intends to support the broadband.

In the LTE TDD system, a UE can feed back multiple ACK/NACKs formultiple PDSCHs to a BS. This is because the UE can receive the multiplePDSCHs in multiple subframes, and can transmit ACK/NACK for the multiplePDSCHs in one subframe. In this case, there are two types of ACK/NACKtransmission methods as follows.

The first method is ACK/NACK bundling. The ACK/NACK bundling is aprocess of combining ACK/NACK bits for multiple data units by using alogical AND operation. For example, if the UE decodes all the multipledata units successfully, the UE transmits only one ACK bit. Otherwise,if the UE fails in decoding (or detecting) any one of the multiple dataunits, the UE may transmit NACK or may transmit no signal as ACK/NACK.

The second method is ACK/NACK multiplexing. With ACK/NACK multiplexing,the content and meaning of the ACK/NACK for the multiple data units canbe identified by combining a PUCCH resource used in actual ACK/NACKtransmission and one of QPSK modulation symbols.

For example, it is assumed that up to two data units can be transmitted,and one PUCCH resource can carry two bits. It is also assumed that anHARQ operation for each data unit can be managed by one ACK/NACK bit. Inthis case, the ACK/NACK can be identified at a transmitting node (e.g.,a BS) which transmits the data unit according to Table 5 below.

TABLE 5 HARQ-ACK(0), HARQ-ACK(1) n⁽¹⁾ _(PUCCH) b(0), b(1) ACK, ACK n⁽¹⁾_(PUCCH, 1) 1, 1 ACK, NACK/DTX n⁽¹⁾ _(PUCCH, 0) 0, 1 NACK/DTX, ACK n⁽¹⁾_(PUCCH, 1) 0, 0 NACK/DTX, NACK n⁽¹⁾ _(PUCCH, 1) 1, 0 NACK, DTX n⁽¹⁾_(PUCCH, 0) 1, 0 DTX, DTX N/A N/A

In Table 5, HARQ-ACK(i) indicates an ACK/NACK result for a data unit i.In the above example, two data units may exist, i.e., a data unit 0 anda data unit 1. In Table 5, DTX implies that there is no data unittransmission for the HARQ-ACK(i). Alternatively, it implies that areceiving end (e.g., a UE) fails to detect the data unit for theHARQ-ACK(i). n⁽¹⁾ _(PUCCH,X) indicates a PUCCH resource used in actualACK/NACK transmission. There are up to 2 PUCCH resources, that is, n⁽¹⁾_(PUCCH,0) and n⁽¹⁾ _(PUCCH,1). b(0) and b(1) denote 2 bits delivered bya selected PUCCH resource. A modulation symbol transmitted using thePUCCH resource is determined by b(0) and b(1).

For one example, if the receiving end successfully receives two dataunits and decodes the received data units, the receiving end has totransmit two bits b(0) and b(1) in a form of (1, 1) by using a PUCCHresource n⁽¹⁾ _(PUCCH,1). For another example, it is assumed that thereceiving end receives two data units, and in this case, the receivingend fails to decode 1^(st) data unit and successfully decodes 2^(nd)data unit. Then, the receiving end has to transmit (0, 0) by using n⁽¹⁾_(PUCCH,1).

As such, according to a method in which the content (or meaning) ofACK/NACK is linked to a combination of a PUCCH resource and the contentof an actual bit transmitted using the PUCCH resource, ACK/NACKtransmission for the multiple data units is enabled by using a singlePUCCH resource.

In the ACK/NACK multiplexing method, if at least one ACK exists for alldata units, NACK and DTX are basically coupled as NACK/DTX. This isbecause a combination of a PUCCH resource and a QPSK symbol is notenough to cover all ACK/NACK combinations based on decoupling of theNACK and the DTX.

FIG. 13 shows an example of comparing a single-carrier system and acarrier aggregation system.

Referring to FIG. 13, only one carrier is supported for a UE in anuplink and a downlink in the single-carrier system. The carrier may havevarious bandwidths, but only one carrier is assigned to the UE.Meanwhile, multiple component carriers (CCs), i.e., DL CCs A to C and ULCCs A to C, can be assigned to the UE in the carrier aggregation system.For example, three 20 MHz CCs can be assigned to allocate a 60 MHzbandwidth to the UE.

The carrier aggregation system can be divided into a contiguous carrieraggregation system in which carriers are contiguous to each other and anon-contiguous carrier aggregation system in which carriers areseparated from each other. Hereinafter, when it is simply called thecarrier aggregation system, it should be interpreted such that bothcases of contiguous CCs and non-contiguous CCs are included.

A CC which is a target when aggregating one or more CCs can directly usea bandwidth that is used in the legacy system in order to providebackward compatibility with the legacy system. For example, a 3GPP LTEsystem can support a bandwidth of 1.4 MHz, 3 MHz, 5 MHz, 10 MHz, 15 MHz,and 20 MHz, and a 3GPP LTE-A system can configure a broadband of 20 MHzor higher by using only the bandwidth of the 3GPP LTE system.Alternatively, the broadband can be configured by defining a newbandwidth without having to directly use the bandwidth of the legacysystem.

A frequency band of a wireless communication system is divided into aplurality of carrier frequencies. Herein, the carrier frequency impliesa center frequency of a cell. Hereinafter, the cell may imply a downlinkfrequency resource and an uplink frequency resource. Alternatively, thecell may also imply combination of a downlink frequency resource and anoptional uplink frequency resource. In general, if carrier aggregation(CA) is not considered, uplink and downlink frequency resources canalways exist in pair in one cell.

In order to transmit and receive packet data through a specific cell,the UE first has to complete configuration of the specific cell. Herein,the configuration implies a state of completely receiving systeminformation required for data transmission and reception for the cell.For example, the configuration may include an overall procedure thatrequires common physical layer parameters necessary for datatransmission and reception, MAC layer parameters, or parametersnecessary for a specific operation in an RRC layer. A cell of whichconfiguration is complete is in a state capable of immediatelytransmitting and receiving a packet upon receiving only informationindicating that packet data can be transmitted.

The cell in a state of completing its configuration can exist in anactivation or deactivation state. Herein, the activation implies thatdata transmission or reception is performed or is in a ready state. TheUE can monitor or receive a control channel (i.e., PDCCH) and a datachannel (PDSCH) of an activated cell in order to confirm a resource(e.g., frequency, time, etc.) allocated to the UE.

The deactivation implies that transmission or reception of traffic datais impossible and measurement or transmission/reception of minimuminformation is possible. The UE can receive system information (SI)required to receive a packet from a deactivated cell. On the other hand,in order to confirm the resource (e.g., frequency, time, etc.) allocatedto the UE, the UE does not monitor or receive a control channel (i.e.,PDCCH) and a data channel (i.e., PDSCH) of the deactivated cell.

A cell can be classified into a primary cell, a secondary cell, aserving cell.

The primary cell implies a cell that operates at a primary frequency.Further, the primary cell implies a cell in which the UE performs aninitial connection establishment procedure or a connectionre-establishment procedure with respect to the BS or a cell indicated asthe primary cell in a handover procedure.

The secondary cell implies a cell that operates at a secondaryfrequency. Once an RRC connection is established, the secondary cell isused to provide an additional radio resource.

The serving cell is configured with the primary cell in case of a UE ofwhich CA is not configured or which cannot provide the CA. If the CA isconfigured, the term ‘serving cell’ is used to indicate a set consistingof one or a plurality of cells among primary cells or all secondarycells.

That is, the primary cell implies one serving cell that providessecurity input and NAS mobility information in an RRC establishment orre-establishment state. According to UE capabilities, it can beconfigured such that at least one cell constitutes a serving celltogether with the primary cell, and in this case, the at least one cellis called the secondary cell.

Therefore, a set of serving cells configured only for one UE can consistof only one primary cell, or can consist of one primary cell and atleast one secondary cell.

A primary component carrier (PCC) denotes a CC corresponding to aprimary cell. The PCC is a CC that establishes an initial connection (orRRC connection) with the BS among several CCs. The PCC serves forconnection (or RRC connection) for signaling related to a plurality ofCCs, and is a CC that manages UE context which is connection informationrelated to the UE. In addition, the PCC establishes connection with theUE, and thus always exists in an activation state when in an RRCconnected mode.

A secondary component carrier (SCC) denotes a CC corresponding to asecondary cell. The SCC is a CC allocated to the UE in addition to thePCC. The SCC is an extended carrier used by the UE for additionalresource allocation or the like in addition to the PCC, and can bedivided into an activation state and a deactivation state.

A downlink CC corresponding to the primary cell is called a downlinkprimary component carrier (DL PCC), and an uplink CC corresponding tothe primary cell is called an uplink primary component carrier (UL PCC).In addition, in a downlink, a CC corresponding to the secondary cell iscalled a downlink secondary CC (DL SCC). In an uplink, a CCcorresponding to the secondary cell is called a uplink secondary CC (DLSCC).

The primary cell and the secondary cell have the following features.

First, the primary cell is used for PUCCH transmission.

Second, the primary cell is always activated, whereas the secondary cellis a cell which is activated/deactivated according to a specificcondition.

Third, when the primary cell experiences a radio link failure (RLF), RRCre-establishment is triggered, whereas when the secondary cellexperiences the RLF, the RRC re-establishment is not triggered.

Fourth, the primary cell can change by a handover procedure accompaniedby a random access channel (RACH) procedure or security keymodification.

Fifth, non-access stratum (NAS) information is received through theprimary cell.

Sixth, the primary cell always consists of a pair of a DL PCC and a ULPCC.

Seventh, for each UE, a different CC can be configured as the primarycell.

Eighth, a procedure such as reconfiguration, adding, and removal of theprimary cell can be performed by an RRC layer. When adding a newsecondary cell, RRC signaling can be used for transmission of systeminformation of a dedicated secondary cell.

A DL CC can construct one serving cell. Further, the DL CC can beconnected to a UL CC to construct one serving cell. However, the servingcell is not constructed only with one UL CC.

Activation/deactivation of a CC is equivalent to the concept ofactivation/deactivation of a serving cell. For example, if it is assumedthat a serving cell 1 consists of a DL CC 1, activation of the servingcell 1 implies activation of the DL CC 1. If it is assumed that aserving cell 2 is configured by connecting a DL CC 2 and a UL CC 2,activation of the serving cell 2 implies activation of the DL CC 2 andthe UL CC 2. In this sense, each CC can correspond to a cell.

The number of CCs aggregated between a downlink and an uplink may bedetermined differently. Symmetric aggregation is when the number of DLCCs is equal to the number of UL CCs. Asymmetric aggregation is when thenumber of DL CCs is different from the number of UL CCs. In addition,the CCs may have different sizes (i.e., bandwidths). For example, if 5CCs are used to configure a 70 MHz band, it can be configured such as 5MHz CC(carrier #0)+20 MHz CC(carrier #1)+20 MHz CC(carrier #2)+20 MHzCC(carrier #3)+5 MHz CC(carrier #4).

As described above, the carrier aggregation system can support multiplecomponent carriers (CCs) unlike a single carrier system. That is, one UEcan receive multiple PDSCHs through multiple DL CCs. In addition, the UEcan transmit ACK/NACK for multiple PDSCHs through one UL CC (e.g., ULPCC). That is, since only one PDSCH is received in one subframe in theconventional single carrier system, it has been enough to transmit onlyup to two pieces of HARQ ACK/NACK (hereinafter, simply referred to asACK/NACK for convenience of explanation) information. However, since thecarrier aggregation system can transmit ACK/NACK for multiple PDSCHsthrough one UL CC, an ACK/NACK transmission method is required for this.

1. Multi-bit ACK/NACK Transmission

Herein, multi-bit ACK/NACK implies an ACK/NACK bit for multiple PDSCHs.If a UE operates in an SU-MIMO mode in a DL CC and receives twocodewords, then ACK/ACK, ACK/NACK, NACK/ACK, and NACK/NACK are presentfor the two codewords with respect to the DL CC, and if DTX is includedas a message indicating that the PDCCH is not received, 5 feedbackstates are present in total. If the UE does not operate in the SU-MIMOmode and receives only one codeword, three feedback states (i.e., ACK,NACK, DTX) are present. Therefore, if the UE configures up to 5 DL CCsand operates in the SU-MIMO mode in all DL CCs, up to 5⁵ (=3125)feedback states can be present. This can be expressed by 12 bits.Alternatively, if NACK and DTX are mapped to the same feedback state inall DL CCs, up to 4⁵ feedback states are present, which can be expressedby 10 bits. As such, there is a need for a method of transmittingmulti-bit ACK/NACK for multiple PDSCHs.

Method 1-1: Method Based on PUCCH Format 2

In this method, multi-bit ACK/NACK information on PDSCHs of multiple DLCCs is transmitted based on the PUCCH format 2.

FIG. 14 shows a method based on the PUCCH format 2.

Referring to FIG. 14, a multi-bit ACK/NACK information bit (e.g., a10-bit ACK/NACK information bit) is channel-coded, for example, with acoding rate of ½, thereby generating 20 ACK/NACK coded bits. AReed-Muller code can be used in the channel coding. The RM code may befound in Table 4 above. QPSK constellation mapping is performed on theACK/NACK coded bit to generate QPSK modulation symbols (e.g., d₀ to d₄in a slot 0). Each QPSK modulation symbol is modulated by using a cyclicshift of a base RS sequence having a length of 12, and is then subjectedto OFDM modulation. Then, the resultant symbol is transmitted in each of10 SC-FDMA symbols in a subframe. 12 equally-spaced cyclic shifts allow12 different UEs to be orthogonally multiplexed on the same PUCCH RB. ADM RS sequence applied to the SC-FDMA symbols 1 and 5 may be the base RSsequence having a length of 12.

When the multi-bit ACK/NACK information is transmitted by using themethod based on the PUCCH format 2, any one of the following two channelcoding methods can be used.

Method 1-1-1: Fast Codebook Adaptation

In this method, the multi-bit ACK/NACK to be transmitted in a subframeis mapped sequentially starting from a first basis of an RM code (i.e.,a first column vector) to optimize ACK/NACK transmission performance formultiple DL CCs. That is, this method performs channel coding in such amanner that, in a multi-bit ACK/NACK information bit stream, a firstACK/NACK information bit (i.e., MSB) is mapped to the first basis of theRM code and a next ACK/NACK information bit is mapped to a second basisof the RM code. Since the RM code is designed to have optimalperformance when the same payload is channel-coded by sequentiallymapping from a first basis, optimal performance can be shown byperforming mapping between the ACK/NACK and the basis of the RM code.However, when codeword DTX occurs, a payload size may be misalignedbetween the BS and the UE in this method. Therefore, the BS preferablyreports the total number of PDSCH codewords and/or a PDSCH counter byusing a downlink assignment index (DAI) and a DL control signal.

Method 1-1-2: Slow Codebook Adaptation

In this method, the multi-bit ACK/NACK is mapped to a basis of an RMcode which is fixed semi-statically when it is mapped to the basis ofthe RM code. For example, the UE can perform channel coding by mapping acorresponding ACK/NACK information bit per codeword of each DL CC to thebasis of the RM code determined semi-statically. The UE performs channelcoding by mapping an ACK/NACK information bit regarding a PDSCH receivedper frame to the basis of the predetermined RM code. The BS can performdecoding by assuming a payload suitable for the number of codewords of aDL CC configured in ACK/NACK decoding. Therefore, ACK/NACK can bedecoded without occurrence of payload misalignment. However, since anoptimized RM code cannot be used in this method, performance maydeteriorate to some extent in comparison with fast codebook adaptation.However, this method has an advantage in that there is no need to reportthe total number of PDSCH codewords and/or the PDSCH counter by using aDL control signal such as DAI.

FIG. 15 shows an example of the aforementioned fast codebook adaptationand slow codebook adaptation.

It is assumed in FIG. 15 that 5 DL CCs are assigned to a UE, and up totwo codewords can be received in each of a DL CC 1 to a DL CC 4 (i.e., aMIMO mode), and only one codeword can be received in a DL CC 5 (i.e., anon-MIMO mode). In addition, it is also assumed that the UE receives aPDSCH through the DL CC 1 and the DL CC 3 in any subframe. A basis(i.e., a column vector) of an RM code is denoted by b0, b1, . . . , b10.

In this case, when using fast codebook adaptation, as shown n FIG. 15(a), an ACK/NACK information bit for a codeword 1 (C1) of the DL CC 1 ismapped to a first basis b0, and an ACK/NACK information bit for acodeword 2 (C2) of the DL CC 1 is mapped to a second basis b1. Further,an ACK/NACK information bit for a codeword 1 (C1) of the DL CC 2 ismapped to a third basis b2, and an ACK/NACK information bit for acodeword 2 (C2) of the DL CC 2 is mapped to a fourth basis b3.

That is, an ACK/NACK information bit for a codeword of each DL CC issequentially mapped to a basis of an RM code.

If slow codebook adaptation is used in the above case, as shown in FIG.15( b), the ACK/NACK information bit for the codeword of each DL CC ismapped to a basis of a predetermined RM code. For example, codewords 1and 2 of the DL CC 1 can be mapped in advance to b0 and b1, codewords 1and 2 of the DL CC 2 can be mapped in advance to b2 and b3, codewords 1and 2 of the DL CC 3 can be mapped in advance to b4 and b5, codewords 1and 2 of the DL CC 4 can be mapped in advance to b6 and b7, andcodewords 1 and 2 of the DL CC 5 can be mapped in advance to b8 and b9.Then, under the aforementioned assumption, channel coding is performedsuch that the ACK/NACK information bit is mapped to the basispredetermined as shown in FIG. 15( b).

Method 1-2: Method Based on Block Spreading

The method based on block spreading implies a method of multiplexing amodulation symbol sequence obtained by modulating multi-bit ACK/NACK byusing a block spreading code. The method based on the block spreadingcan use SC-FDMA. Herein, the SC-FDMA is a transmission scheme in whichIFFT is performed after DFT spreading is performed. The SC-FDMA is alsocalled DFT-spread OFDM (DFT-s OFDM). A peak-to-average power ratio(PAPR) to a cubic metric (CM) can be decreased in the SC-FDMA. Themethod based on block spreading can be used to multiplex the multi-bitACK/NACK for multiple UEs in the same resource block.

FIG. 16 shows an example of a method based on block spreading.

Referring to FIG. 16, a modulation symbol sequence {d1, d2, . . . } isspread by applying a block spreading code. Herein, the modulation symbolsequence may be sequence of modulation symbols obtained in such a mannerthat multi-bit ACK/NACK information bits are channel-coded (using an RMcode, a TBCC, a punctured RM code, etc.) to generate ACK/NACK codedbits, and the ACK/NACK coded bits are modulated (e.g., using QPSK). Inthis case, the ACK/NACK coded bits can be generated by applying theaforementioned fast codebook adaptation or slow codebook adaptation. Inaddition, although a case where three RS symbols exist in one slot isshown in the example of FIG. 16, two RS symbols may be present, and inthis case, a block spreading code with a length 5 can be used. Table 6below shows an example of the block spreading code.

TABLE 6 index N_(SF) ^(PUCCH) = 5 N_(SF) ^(PUCCH) = 4 0 [1 1 1 1 1] [+1+1 +1 +1] 1 [1 e^(j2π/5) e^(j4π/5) e^(j6π/5) e^(j8π/5)] [+1 −1 +1 −1] 2[1 e^(j4π/5) e^(j8π/5) e^(j2π/5) e^(j6π/5)] [+1 −1 −1 +1] 3 [1 e^(j6π/5)e^(j2π/5) e^(j8π/5) e^(j4π/5)] [+1 +1 −1 −1] 4 [1 e^(j8π/5) e^(j6π/5)e^(j4π/5) e^(j2π/5)] —

In Table 6 above, N^(PUCCH) _(SF) denotes a spreading factor (SF).

Method 1-3: SF Reduction

This method is modified from PUCCH formats 1a/1b used in LTE rel-8 as amethod of decreasing an SF of an orthogonal code to allow one UE to beable to multiplex a greater amount of ACK/NACK information to the sameresource block. For example, since the SF is 4 in the conventional PUCCHformats 1a/1b, the number of ACK/NACK modulation symbols that can betransmitted in one slot is 1. However, the number of ACK/NACK modulationsymbols that can be transmitted by one UE in one slot is increased to 2or 4 by decreasing the SF to 2 or 1. Therefore, the greater amount ofACK/NACK information can be transmitted.

Method 2: Multi-Code ACK/NACK Transmission

In this method, transmission is performed by extending the conventionalACK/NACK transmission, i.e., a method of transmitting ACK/NACKinformation by using the PUCCH formats 1a/1b, to multiple PUCCHs. Forexample, if a UE receives N PDSCHs in total, N PUCCHs can be transmittedsimultaneously by using the PUCCH formats 1a/1b.

Method 3: ACK/NACK Multiplexing (ACK/NACK Selection)

In this method, ACK/NACK multiplexing used in LTE rel-8 TDD is appliedto FDD of a carrier aggregation environment. In TDD, ACK/NACKinformation on a PDSCH received in multiple subframes is transmitted inone subframe. This mechanism is applied to FDD. That is, upon receivingmultiple PDSCHs in multiple DL CCs, a UE transmits ACK/NACK by using one(or more) PUCCH (i.e., PUCCH format 1b). In other words, this method isa method of carrying information by using two types of hypotheses, i.e.,which PUCCH channel is used in transmission among several PUCCH channelscapable of ACK/NACK transmission for multiple PDSCHs received inmultiple DL CCs, and which value is used in transmission as a symbolvalue (i.e., QPSK or M-PSK) of the channel.

In a method described hereinafter, a UE multiplexes and transmitsdifferent uplink control information (UCI) in a carrier aggregationsystem. For example, the UE can perform multiplexing between ACK/NACKand SR and between ACK/NACK and CQI and then can transmit themultiplexed signal in the carrier aggregation system.

First, a method of multiplexing SR and ACK/NACK for multiple PDSCHreceived in multiple DL CCs will be described.

Method 4-1: RS Symbol Modulation

In this method, SR information is transmitted by being phase-modulatedto an RS symbol of an ACK/NACK signal in an SR subframe in which an SRcan be transmitted (herein, the ACK/NACK signal implies an ACK/NACKsignal transmitted by using any one of the aforementioned methods 1 to3). That is, in this method, 1-bit SR information is multiplexed byallowing some RS symbols and the remaining RS symbols to be in phase orout phase among multiple RS symbols used in ACK/NACK signaltransmission. In addition, if there is no ACK/NACK signal transmissionin the SR subframe, the SR information is transmitted using the PUCCHformat 1 type (i.e., on-off keying) similarly to the conventionalmethod. In this method 4-1, RS modulation adaptation can be determinedaccording to which method is used in transmission among theaforementioned methods 1-1 to 1-3, method 2, and method 3.

When the ACK/NACK signal is transmitted by using the aforementionedmethod 1-1, two RS symbols are used per one slot. Therefore, it can betransmitted by modulating an SR to a phase difference between a first RSsymbol and a second RS symbol in a slot.

When the ACK/NACK signal is transmitted by using the aforementionedmethod 1-2, two or three RS symbols are used per one slot. If two RSsymbols are used, an SR is modulated to a phase difference between thetwo RS symbols. If three RS symbols are used, an SR is modulated to aphase difference between two consecutive RS symbols. That is, an SR ismodulated to a phase difference between a first RS symbol and a secondRS symbol in a slot or between the second RS symbol and a third RSsymbol.

When the ACK/NACK signal is transmitted by using the aforementionedmethod 1-3, method 2, or method 3, three RS symbols are used per oneslot. In this case, an SR is preferably modulated to a phase differencebetween two consecutive RS symbols.

In addition, when ACK/NACK is transmitted by applying the aforementionedmethod 2, RS modulation is preferably applied to all PUCCHs for SRdetection in multiple PUCCH transmission.

Since an SR reception rate may deteriorate when SR information ismodulated to a phase difference between RS symbols and demodulationperformance may deteriorate when performing ACK/NACK demodulation asdescribed above, the UE can transmit an RS symbol by boosting power ofthe RS symbol in an SR subframe to avoid performance deterioration.

Method 4-2: Fallback

In this method, when SR transmission is performed in an SR subframesimultaneously with ACK/NACK transmission for multiple PDSCHs, ACK/NACKinformation is bundled to create a 1-bit or 2-bit bundled ACK/NACK bit,and the bundled ACK/NACK bit is transmitted using a resource reservedfor SR transmission. If SR transmission is not necessary in the SRsubframe, the ACK/NACK information can be transmitted by using theaforementioned methods 1 to 3. If ACK/NACK transmission is not necessaryin the SR subframe, the SR information is transmitted using the PUCCHformat 1 (i.e., on-off keying) through an SR resource.

Any one of the following four methods can be used as a method ofbundling ACK/NACK information in the present invention.

1) Method of transmitting ACK/NACK bits for all PDSCHs by performing alogical AND operation to make the ACK/NACK bits one ACK/NACK bit.

2) Method of performing bundling per codeword by considering an SU-MIMOmode. That is, in this method, ACK/NACK for a first codeword of each DLCC is bundled to create one ACK/NACK, and ACK/NACK for a second codewordof each DL CC is bundled to create another ACK/NACK. In this case, ifany DL CC operates not in the SU-MIMO mode but in a single codewordmode, ACK/NACK for a codeword of the DL CC can be bundled together whenACK/NACK bundling is performed on the first codeword.

3) Method of bundling ACK/NACK information according to a transmissionmode of each DL CC. For example, in this method, ACK/NACK informationfor DL CCs in the single codeword mode is bundled among DL CCs to createone ACK/NACK, and ACK/NACK information for DL CCs in the SU-MIMO mode isbundled to create two ACK/NACKs.

4) Method of dividing multiple DL CCs by a predetermined group andtransmitting ACK/NACK information for all DL CCs in each group bybundling the ACK/NACK information. For example, the number of groups maybe 2, and can be reported in advance to the UE by using a higher layersignal (RRC signal), a CC activation/deactivation signal, etc.

In the aforementioned method 4-2, ACK/NACK for a PDSCH transmitted in aspecific DL CC, e.g., a DL PSS, in the SR subframe can be transmittedusing the conventional method (i.e., PUCCH formats 1a/1b), and ACK/NACKfor the remaining DL CCs can be transmitted using the aforementionedmethods 1 to 3. For example, if SR transmission is necessary, theACK/NACK for the specific DL CC is transmitted through a resourcereserved for SR transmission, and the ACK/NACK for the remaining DL CCscan be transmitted using the aforementioned methods 1 to 3.

Method 4-3: Joint Coding of ACK/NACK and SR

As described above, in LTE Rel-8, SR transmission and ACK/NACKtransmission may collide in a subframe capable of SR transmission whenthere is no PUSCH transmission. In this case, an SR resource is used inACK/NACK transmission. If SR transmission is not necessary in thesubframe, ACK/NACK is transmitted using a resource reserved forACK/NACK, and no signal is transmitted for the SR resource. Meanwhile,since ACK/NACK for multiple PDSCHs is transmitted in a carrieraggregation system such as an LTE-A system, if there is no PUSCHtransmission, it is necessary to modify the conventional SR and ACK/NACKmultiplexing method.

In this method, SR information is multiplexed by adding one bit to apayload of multi-bit ACK/NACK in an SR subframe. For example, in thismethod, if an N-bit information bit payload is channel-coded forACK/NACK transmission in a subframe other than the SR subframe and thusan M-bit (M≧N) coded bit is generated and transmitted, SR information isadded in the SR subframe and thus an (N+1) bit information bit payloadis channel-coded, thereby generating and transmitting an M-bit (M≧N)coded bit. That is, SR and ACK/NACK are transmitted by using jointcoding.

Alternatively, in order to avoid increase in the payload of theinformation bit in the SR subframe, the number of bits of the ACK/NACKinformation or the number of states can be decreased, and then one bitfor the SR can be added, thereby being able to perform transmissionwithout the increase in the payload of the information bit.

Any one of the following three methods can be used as a method ofcompressing ACK/NACK information to decrease the number of bits of theACK/NACK information or the number of states.

1) Method of not transmitting a DTX state: that is, the DTX state can beprocessed as NACK. For example, although one of five states (i.e.,ACK/ACK, ACK/NACK, NACK/ACK, NACK/NACK, DTX) have to be reported if acertain DL CC operates in an SU-MIMO mode, the number of states can bedecreased to four if the DTX state is transmitted as NACK. Likewise, bytransmitting DTX as a NACK state in a DL CC operating in a singlecodeword mode, three states (i.e., ACK, NACK, DTX) can be decreased totwo states (i.e., ACK, NACK). As such, the method of decreasing the DTXstates can apply to either all DL CCs or some CCs.

2) When there is a DL CC operating in an SU-MIMO mode, spatial bundlingis used. The spatial bundling decreases the number of states byperforming bundling between ACK/NACKs for codewords of different DL CCs.The spatial bundling can also apply to either all DL CCs or some DL CCs.

3) Combination of the above methods 1) and 2)

FIG. 17 shows joint coding of ACK/NACK and SR in a carrier aggregationsystem.

Referring to FIG. 17, a UE generates a bit-stream by concatenating afirst UCI information bit and a second UCI information bit, and performschannel coding on the generated bit-stream. The channel coding may beany one of simple repetition, simplex coding, RM coding, punctured RMcoding, tail-biting convolutional coding (TBCC), low density paritychecking (LDPC) coding, turbo coding, etc. The first UCI information bitmay be ACK/NACK, and the second UCI information bit may be SR (1 bit).That is, an SR information bit can be appended to the end of theACK/NACK information bits. It can be expressed that the SR informationbit is concatenated to a least significant bit (LSB) in a bit-stream ofthe ACK/NACK and the SR. Concatenating of the SR information bit to theLSB implies that the SR information bit is mapped to a rightmost basis.i.e., a rightmost column, of an RM code when the SR information bit isjointly coded with the ACK/NACK information bit.

Alternatively, the first UCI information bit may be SR (1 bit), and thesecond UCI information bit may be ACK/NACK. It can be expressed that theSR information bit is appended to a most significant bit (MSB) in abit-stream of the ACK/NACK and the SR. Then, a first basis b0 of the RMcode and the SR information bit are mapped when performing channelcoding.

It is assumed in FIG. 18 and FIG. 19 that 5 DL CCs are assigned to a UE,and up to two codewords can be received in each of a DL CC 1 to a DL CC4 (i.e., a MIMO mode), and only one codeword can be received in a DL CC5 (i.e., a non-MIMO mode). In addition, it is also assumed that the UEreceives a PDSCH through the DL CC 1 and the DL CC 3 in any subframe. Abasis (i.e., a column vector) of an RM code is denoted by b0, b1, . . ., b10.

FIG. 18 shows a process for locating an SR information bit to an LSB andperforming channel coding in case of using slow codebook adaptation.

Referring to FIG. 18, when ACK/NACK is transmitted using theaforementioned slow codebook adaptation, the SR information bit can belocated to the LSB. Then, channel coding is performed by mapping the SRinformation bit to a basis b9 which comes next to RM code bases b0 to b8reserved for ACK/NACK transmission. In doing so, without having tochange mapping of the basis of the RM code and the ACK/NACKsemi-statically fixed, only one more RM code basis is added for the SRinformation bit. Therefore, there is an advantage in that decoding canbe performed in a BS without having to modify the conventional mappingof the ACK/NACK and the basis of the RM code.

FIG. 19 shows an example of a process for locating an SR information bitto an MSB and performing channel coding when using slow codebookadaptation.

Referring to FIG. 19, the SR information bit is located to an MSB whenthe SR information bit and an ACK/NACK information bit are jointlycoded. This implies that it is mapped to a leftmost basis of an RM code.For example, when the ACK/NACK information bit and the SR informationbit are transmitted using the PUCCH format 2, the SR information bit ismapped to a first basis of the RM code. When ACK/NACK is transmittedusing the aforementioned slow codebook adaptation (i.e., when theACK/NACK per CC and the basis of the RM code are fixed semi-statically),a probability that channel coding can be performed with an optimized RMcode is increased if the SR information bit is located to the MSB. Inother words, since there is a high probability that bases used in RMencoding (in comparison with a method of assigning the SR informationbit to the LSB) are sequentially used from a first basis, it isadvantageous in terms of RM code performance.

As such, since the SR information bit is mapped to a first basis in anSR subframe when ACK/NACK is transmitted using slow codebook adaptation,mapping of the basis of the RM code and the ACK/NACK determinedsemi-statically can change. Therefore, the UE can implicitly shiftmapping of the ACK/NACK information bit and the basis of the RM code.

In addition, if it is not the SR subframe, the conventionalsemi-statically mapping of the RM code basis and ACK/NACK informationbit can be directly used while allowing implicit shift of the mapping ofthe ACK/NACK information bit and the RM code basis in order to ensuremapping of the SR information bit and the RM code basis in the SRsubframe.

FIG. 20 shows an example of a process in which a UE performs jointcoding by combining different UCI and then maps it to a resource blockof each slot. ACK/NACK and SR are shown as an example of the differentUCI in FIG. 20.

Referring to FIG. 20, channel coding is performed on a bit-streamconsisting of an ACK/NACK information bit and an SR information bit foreach CC (step S201). The SR information bit can be concatenated to alast part of the ACK/NACK information bit. An RM code may be used inchannel coding. Table 7 below shows an example of the RM code applied tothe bit-stream consisting of the ACK/NACK information bit and the SRinformation bit.

TABLE 7 i M_(i, 0) M_(i, 1) M_(i, 2) M_(i, 3) M_(i, 4) M_(i, 5) M_(i, 6)M_(i, 7) M_(i, 8) M_(i, 9) M_(i, 10) 0 1 1 0 0 0 0 0 0 0 0 1 1 1 1 1 0 00 0 0 0 1 1 2 1 0 0 1 0 0 1 0 1 1 1 3 1 0 1 1 0 0 0 0 1 0 1 4 1 1 1 1 00 0 1 0 0 1 5 1 1 0 0 1 0 1 1 1 0 1 6 1 0 1 0 1 0 1 0 1 1 1 7 1 0 0 1 10 0 1 1 0 1 8 1 1 0 1 1 0 0 1 0 1 1 9 1 0 1 1 1 0 1 0 0 1 1 10 1 0 1 0 01 1 1 0 1 1 11 1 1 1 0 0 1 1 0 1 0 1 12 1 0 0 1 0 1 0 1 1 1 1 13 1 1 0 10 1 0 1 0 1 1 14 1 0 0 0 1 1 0 1 0 0 1 15 1 1 0 0 1 1 1 1 0 1 1 16 1 1 10 1 1 1 0 0 1 0 17 1 0 0 1 1 1 0 0 1 0 0 18 1 1 0 1 1 1 1 1 0 0 0 19 1 00 0 0 1 1 0 0 0 0 20 1 0 1 0 0 0 1 0 0 0 1 21 1 1 0 1 0 0 0 0 0 1 1 22 10 0 0 1 0 0 1 1 0 1 23 1 1 1 0 1 0 0 0 1 1 1 24 1 1 1 1 1 0 1 1 1 1 0 251 1 0 0 0 1 1 1 0 0 1 26 1 0 1 1 0 1 0 0 1 1 0 27 1 1 1 1 0 1 0 1 1 1 028 1 0 1 0 1 1 1 0 1 0 0 29 1 0 1 1 1 1 1 1 1 0 0 30 1 1 1 1 1 1 1 1 1 11 31 1 0 0 0 0 0 0 0 0 0 0

An encoding information bit generated as a result of channel coding canbe rate-matched by considering a resource to be mapped and a modulationsymbol order. For inter-cell interference (ICI) randomization withrespect to the generated encoding information bit, cell-specificscrambling using a scrambling code corresponding to a cell ID orUE-specific scrambling using a scrambling code corresponding to a UE ID(for example, a radio network temporary identifier (RNTI)) can beapplied (step S202).

The scrambled encoding information bit is modulated by the use of amodulator (step S203). A modulation symbol sequence consisting of a QPSKsymbol configured by modulating the scrambled encoding information canbe generated. The QPSK symbol may be a complex modulation symbol havinga complex value.

With respect to QPSK symbols in each slot, discrete Fourier transform(DFT) for generating a single carrier waveform is performed in each slot(step S204).

With respect to the QPSK symbol subjected to DFT, block-wise spreadingis performed in an SC-FDMA symbol level by using a predeterminedspreading code or spreading code determined through dynamic signaling orradio resource control (RRC) signaling (step S205). That is, amodulation symbol sequence is spread by using an orthogonal sequence togenerate a spread sequence. The spread sequence includes a sequencegenerated by multiplying some modulation symbols included in themodulation symbol sequence by an element of the orthogonal sequence. Thegenerated sequence can be transmitted by being assigned to eachsubcarrier in an SC-FDMA symbol. The number of some modulation symbolsmay be equal to the number of subcarriers included in a resource block.

A spreading code may be found in Table 6 above. A spreading factor ofthe spreading code can vary depending on a system, and can bepredetermined or can be reported to the UE through DCI or RRC signaling.A format of such control channels is called the PUCCH format 3.

The spread sequence is mapped to a subcarrier in the resource block(steps S206 and S207). Thereafter, it is converted into a time-domainsignal by using inverse fast Fourier transform (IFFT), is then attachedwith a CP, and is then transmitted via a radio frequency (RF) unit.

FIG. 21 shows an example of mapping spread QPSK symbols to a subcarrierin a resource block in a normal CP.

Referring to FIG. 21, each of QPSK symbols d0 to d11 and d12 to d23 istime-spread across 5 SC-FDMA symbols in one slot. A reference signal ismapped to 2^(nd) and 6^(th) SC-FDMA symbols in each slot. This is thesame as a location to which the reference signal is mapped when usingthe PUCCH formats 2/2a/2b in LTE rel-8.

Method 4-4: New Resource Allocation for SR

In this method, in a case where a UE transmits multi-bit ACK/NACK byusing the aforementioned method 1, when an SR resource is reserved forSR transmission, a resource capable of transmitting the multi-bitACK/NACK is reserved instead of reserving a PUCCH format 1/1a/1bresource. That is, in this method, ACK/NACK is transmitted using amulti-bit ACK/NACK resource if the SR is not transmitted in an SRsubframe, and multi-bit ACK/NACK is transmitted using a resourcereserved for SR transmission if the SR is transmitted in the SRsubframe. In this case, a resource for the SR is preferably reservedwhen the UE is configured to operate in a multi-bit ACK/NACK mode.

Method 4-5: Additional Resource Allocation for SR

When a UE transmits ACK/NACK by using the aforementioned method 1-2,since a symbol for transmitting ACK/NACK is multiplexed with anorthogonal code, up to 4 or 5 pieces of ACK/NACK information of the UEcan be multiplexed. On the other hand, an RS symbol has two types ofresources that can be multiplexed, i.e., cyclic shift (CS) of an RSsequence and an orthogonal code of an RS. Therefore, RS multiplexingcapability may be larger. In this method, SR information can betransmitted using an RS multiplexing resource (i.e., the CS of the RSsequence and/or the orthogonal code of the RS) that can be additionallyused. For example, the UE can be allowed to use multiple (preferably 2)RS sequence CSs in the SR subframe so that SR information (i.e.,negative/positive SR) can be transmitted according to which RS sequenceCS is used among the multiple RS sequence CSs. For example, when the UEtransmits an RS by using an RS sequence CS #1, a BS may recognize it asnegative SR, and when the UE transmits an RS by using an RS sequence CS#2, the BS may recognize it as positive SR. The BS can detect the SR bydetecting reception energy of a plurality of available RS sequence CSs.

In another exemplary embodiment, SR information can be transmitted usingan orthogonal code of an RS. Two or three RS symbols can be used in oneslot in the aforementioned method 1-2. Therefore, SR information(negative/positive SR) can be transmitted according to which orthogonalcode is used between a length-2 orthogonal code and a length-3orthogonal code. The BS can receive the SR information by detectingenergy of available orthogonal codes of the RS. In addition, it is alsopossible to consider an SR transmission method using a combination ofthe aforementioned two types of resources (i.e., the CS of the RSsequence and the orthogonal code of the RS).

A resource (i.e., the CS of the RS sequence and/or the orthogonal codeof the RS) additionally used for SR transmission is preferably allocatedin advance to the UE by the BS so that the UE can use the resource forthe SR subframe.

Method 4-6: Piggyback of ACK/NACK Only for Specific CC

In this method, for SR transmission, a UE first ensures an SR resource(e.g., a resource capable of PUCCH format 1a/1b transmission). If SRtransmission is not necessary in an SR subframe, ACK/NACK is transmittedusing the aforementioned methods 1, 2, and 3 for example. Otherwise, ifthe SR transmission needs to be transmitted in the SR subframe, onlyACK/NACK information for a specific DL CC(s) (e.g., a DL PCC) istransmitted by modulating it to an SR resource by using of BPSK or QPSKmodulation according to the PUCCH formats 1a/1b. If ACK/NACK of adifferent DL CC other than the specific DL CC is present, ACK/NACKtransmission of the different DL CC can be dropped.

When the UE transmits ACK/NACK according to the present invention, theBS can assign a specific number of DL grants to prevent dropping ofunnecessary ACK/NACK transmission. Herein, the specific number is lessthan or equal to the maximum number of ACK/NACKs that can be transmittedusing an ensured SR resource (e.g., up to 2 ACK/NACKs in case of thePUCCH formats 1a/1b), and the DL grants are located 4 ms prior to the SRsubframe.

Method 4-7: Higher-Order Modulation

In this method, higher-order modulation (e.g., 8PSK, 16QAM, etc.) isused to modulate ACK/NACK having a greater number of bits than 2 bits toan SR resource, instead of modulation ACK/NACK information having up to2 bits to the SR resource by using BPSK or QPSK similarly to theconventional LTE Rel-8. As a result, the ACK/NACK information having twoor more bits can be modulated to the SR resource. In this method, onlyACK/NACK information for a specific CC(s) can be modulated as describedin the method 4-6. According to this method, a BS can assign a specificnumber of DL grants to compulsively prevent dropping of unnecessaryACK/NACK transmission. Herein, the specific number is less than or equalto the maximum number of ACK/NACKs that can be transmitted using anensured SR resource, and the DL grants are located 4 ms prior to the SRsubframe.

Hereinafter, a method in which ACK/NACK and CQI are multiplexed andtransmitted by a UE in a carrier aggregation system will be described.

As described above, if there is no PUSCH transmission in LTE Rel-8, CQItransmission and ACK/NACK transmission may collide in a CQI subframecapable of periodic CQI transmission. In this case, if simultaneoustransmission of CQI and ACK/NACK is possible, an ACK/NACK signal ismultiplexed by using phase modulation to a second RS symbol in a slot ofa PUCCH format 2 by which CQI is transmitted. However, ACK/NACK formultiple PDSCHs is transmitted in a carrier aggregation system such asan LTE-A system. Therefore, if there is no PUSCH transmission, there isa need to modify the conventional periodic CQI and ACK/NACK multiplexingmethod. Hereinafter, a periodic CQI and ACK/NACK multiplexing methodapplicable to the carrier aggregation system such as the LTE-A systemwill be described.

Method 5-1: Fallback

In this method, a 1-bit or 2-bit bundled ACK/NACK signal is generated bybundling ACK/NACK information for multiple PDSCHs in a CQI subframe, andthereafter the bundled ACK/NACK signal and CQI are transmitted by usingPUCCH formats 2/2a/2b (i.e., by using an RS phase difference). ACK/NACKbundling may use any one of schemes described in the aforementionedmethod 4-2.

In addition, in the method 5-1, ACK/NACK for a specific DL CC can betransmitted using the PUCCH formats 2/2a/2b, and ACK/NACK for a PDSCH ofthe remaining DL CCs other than the specific DL CC can be transmittedusing the aforementioned methods 1 to 3.

Method 5-2: Joint Coding and Bundling

In this method, ACK/NACK information for multiple PDSCHs ischannel-coded together with CQI information in a CQI subframe and isthen transmitted through a physical channel. A UE can transmit ACK/NACKinformation for all received PDSCHs by being jointly coded together withthe CQI without compression. Alternatively, the UE can decrease thenumber of states of the ACK/NACK information or compress the number ofbits and thereafter can transmit the ACK/NACK information by beingjointed coded with the CQI.

A bundled ACK/NACK bit can be generated by bundling ACK/NACK informationfor multiple PDSCHs. The CQI and the bundled ACK/NACK bit can be jointlycoded and then can be transmitted by using (or applying) the PUCCHformat 2. ACK/NACK bundling can use any one of schemes described in theaforementioned method 4-2.

In addition, when ACK/NACK information and CQI are jointly coded, if thenumber of bits of a bit-stream consisting of an ACK/NACK information bitand a CQI information bit is less than or equal to a specific bit number(e.g., the number of bits that can be supported by an RM code whenACK/NACK and CQI are transmitted using the PUCCH format 2 type), theACK/NACK information bit and the CQI information bit are transmitted byperforming joint coding, and otherwise, the CQI information can bedropped and thus only ACK/NACK can be transmitted.

When the UE operates in a time division duplexing (TDD) mode, and the UEuses the aforementioned method based on block spreading for multipleACK/NACK transmission, the following joint coding can be taken intoaccount.

In a subframe in which the CQI is transmitted, the ACK/NACK informationis compressed for each CC (e.g., compressed into 2 bits) to generate thebundled ACK/NACK. The bundled ACK/NACK can be generated into up to 10bits when the UE uses up to 5 CCs by aggregating the CCs. The bundledACK/NACK and the CQI (e.g., up to 11 bits) can be transmitted by beingjointly coded using the PUCCH format 3.

A method of compressing ACK/NACK information for each CC is as follows.A UE transmits information regarding the number of ACKs for a PDSCHreceived in each DL CC and for an SPS release PDCCH in a subframe inwhich CQI is transmitted. In this case, the UE does not detect DTXindicating a failure in receiving of the PDCCH, and can transmit thenumber of ACKs (i.e., an ACK counter) only when there is no NACK for allreceived PDSCHs (or PDCCHs). If there is even one NACK for the allreceived PDCCHs, the ACK counter which is set to a value of 0 can betransmitted.

In addition, the number of ACKs received for each DL CC can betransmitted by being compressed into 2 bits as shown in Table 8 or Table9 below.

TABLE 8 ACK counter HARQ-ACK states 0 00 1 10 2 01 3 11 4 10 5 01 6 11 710 8 01 9 11

TABLE 9 ACK counter HARQ-ACK states 0 00 1 01 2 10 3 11 4 01 5 10 6 11 701 8 10 9 11

Referring to Table 8, if the HARQ-ACK state is ‘10’, the number of ACKsindicated by the ACK counter may be 1, 4, or 7. Since the BS knows thenumber of DL grants assigned to the UE, the BS can predict the number ofACKs indicated by the ACK counter. For example, it is assumed that theBS assigns 3 DL CCs to the UE, and each DL CC operates in an SU-MIMOmode. In this case, if the UE feeds back ‘10’ as the HARQ-ACK state, theBS can predict ‘4’ as the number of ACKs indicated by the ACK counter.This is because there is a low probability that only one ACK istransmitted when 6 codewords are transmitted through 3 DL CCs, and it isimpossible to feed back 7 ACKs. Therefore, the BS can predict that thenumber of ACKs indicated by the ACK counter is 4.

Alternatively, ACK/NACK for DL CCs configured to a MIMO mode can bepreferentially subjected to spatial bundling. That is, the UE cantransmit ACK/NACK by bundling the ACK/NACK for each codeword between DLCCs operating in the SU-MIMO mode. For example, when a DL CC 1 and a DLCC 2 operate in the MIMO mode and are assigned to one UE, the UE canperform spatial bundling in such a manner that ACK/NACK for a codeword 1of the DL CC 1 and ACK/NACK for a codeword 2 of the DL CC 2 are bundledthrough a logical AND operation, and ACK/NACK for a codeword 2 of the DLCC 1 and ACK/NACK for a codeword 2 of the DL CC 2 are bundled throughthe logical AND operation. In this case, the ACK counter may imply thenumber of ACKs subjected to spatial bundling for each DL CC.

Although the UE is set to the TDD mode in the method 5-2, it can belimitedly applied only for a case where DL subframe: UL subframe (i.e.,a ratio or the number of DL subframes with respect to one UL subframe)is not 1:1 (and/or 2:1).

In addition, the method 5-2 can be limitedly applied only for a casewhere the number of ACK/NACK bits transmitted in a subframe other than aCQI subframe in which the UE transmits CQI exceeds 10 bits. The method5-2 may be configurable by a choice of the BS, that is, by using RRCsignaling or L1,2 signaling.

In addition, the method 5-2 can perform ACK/NACK bundling according tothe following embodiment. In a case where ACK/NACK is transmittedwithout spatial bundling in a subframe other than a CQI subframe inwhich CQI is transmitted, if the number of ACK/NACK bits to be fed backwithout bundling in the CQI subframe does not exceed X bits (e.g.,X=10), CQI and ACK/NACK can be jointly coded and can be transmittedusing the PUCCH format 3 without bundling. If the number of ACK/NACKbits to be fed back without bundling in the CQI subframe exceeds the Xbits, spatial bundling is first attempted to generate spatial bundledACK/NACK, and if the number of spatial bundled ACK/NACK bits is lessthan or equal to the X bits, the spatial bundled ACK/NACK and the CQIare transmitted by being jointly coded using the PUCCH format 3. If thenumber of spatial bundled ACK/NACK bits still exceeds the X bits, 2-bitACK/NACK for each CC and CQI can be transmitted by being jointly codedusing the PUCCH format 3 according to the aforementioned ACK counterscheme. In doing so, there is an advantage in that a compression levelof the ACK/NACK can be minimized when the UE transmits the ACK/NACK andthe CQI by performing joint coding.

In addition, ACK/NACK bundling can be performed in the method 5-2according to another embodiment as follows.

If the ACK/NACK is transmitted by being spatial bundled in a subframeother than a CQI subframe in which the CQI is transmitted, in the CQIsubframe in which the CQI is transmitted, if the number of spatialbundled ACK/NACK bits does not exceed X bits (e.g., X=10), the ACK/NACKis transmitted using the PUCCH format 3 after performing joint codingwith the CQI without additional bundling. Otherwise, if the number ofspatial bundled ACK/NACK bits exceeds the X bits, the 2-bit ACK/NACK perCC can be transmitted using the PUCCH format 3 by being jointly codedtogether with the CQI according to the aforementioned ACK counterscheme. This method has an advantage in that a compression level of theACK/NACK can be minimized when the UE transmits the ACK/NACK jointlycoded with the CQI.

If DL subframe: UL subframe is not 2:1 or 1:1, spatial bundling can beperformed on ACK/NACK for a CC configured to operate in the MIMO mode,and thereafter the 2-bit ACK/NACK per CC can be transmitted by beingjointly coded together with the CQI by using the PUCCH format 3according to the aforementioned ACK counter scheme.

If DL subframe:UL subframe is 1:1, the ACK/NACK and the CQI can betransmitted by being jointly coded using the PUCCH format 3 withoutbundling or with only spatial bundling.

Alternatively, if DL subframe:UL subframe is 2:1, the ACK/NACK and theCQI can be transmitted by being jointly coded using the PUCCH format 3without bundling or with only spatial bundling. In this case, thefollowing operation can be taken into account.

If the UE configures two or less DL CCs, the UE may not perform spatialbundling on the ACK/NACK for the DL CC and may transmit the CQI and theACK/NACK by performing joint coding using the PUCCH format 3. If the UEconfigures more than two DL CCs, the UE performs spatial bundling andthen transmits the ACK/NACK joint coded with the CQI by using the PUCCHformat 3.

Method 5-3: Piggyback of Only ACK/NACK for Specific CC

In this method, when CQI and ACK/NACK for multiple DL CCs must betransmitted simultaneously, only ACK/NACK information for a specific DLCC (e.g., a DL PCC) is transmitted using the PUCCH format 2a type (i.e.,a scheme using RS modulation), and ACK/NACK of the remaining CCs otherthan the specific DL CC is dropped.

When using this method, the BS can assign a specific number of DLgrants. Herein, the specific number is less than or equal to the maximumnumber of ACK/NACKs that can be transmitted in an ensured CQI subframe(e.g., up to 2 ACK/NACKs in case of the PUCCH formats 2a/2b), and the DLgrants are located 4 ms prior to the CQI subframe. Then, dropping ofunnecessary ACK/NACK transmission can be compulsively prevented.

Hereinafter, a method of determining transmit power of a PUCCH when a UEtransmits different UCI in a carrier aggregation system will bedescribed.

A case where different UCI is multiplexed by using joint coding will beconsidered. Examples of such a case include a case where ACK/NACK and SRare jointly coded in the aforementioned carrier aggregation system and acase where ACK/NACK and CQI are jointly coded. Herein, a payload of aninformation bit is more increased in the case where the ACK/NACK isjointly coded with the different UCI than the case where joint coding isnot performed. A different power offset value can be assigned per UCIwhen transmitting the different UCI.

Alternatively, when N-bit CQI is transmitted and when the same N-bitsignal is transmitted by combining CQI and ACK/NACK, the different poweroffset value can be assigned to the different UCI since higherperformance is required for the ACK/NACK.

Alternatively, when the ACK/NACK is transmitted by being jointly codedwith the different UCI, the applied power offset value can be set to apower value that satisfies a condition required in ACK/NACKtransmission.

When the ACK/NACK is transmitted by being jointly coded with thedifferent UCI (i.e., SR, CQI, etc.), the power offset value can beassigned by treating the different UCI as if it is the ACK/NACK. Forexample, when the N-bit signal is transmitted by combining the SR andthe ACK/NACK, it is possible to apply the same transmit power as thecase of transmitting only the N-bit ACK/NACK. This is to avoidperformance deterioration of ACK/NACK multiplexed with the differentUCI. For example, if a serving cell c is a primary cell, a PUCCHtransmit power P_(PUCCH) at a subframe i of the UE can be determined byEquation 2 below.

$\begin{matrix}{{P_{PUCCH}(i)} = {\min {\begin{Bmatrix}{{P_{{CMAX},c}(i)},} \\{P_{0{\_ {PUCCH}}} + {PL}_{c} + {h( {n_{CQI},n_{HARQ},n_{SR}} )} + {\Delta_{F\_ {PUCCH}}(F)} + {\Delta_{T \times D}( F^{\prime} )} + {g(i)}}\end{Bmatrix}\lbrack {{dB}\; m} \rbrack}}} & \lbrack {{Equation}\mspace{14mu} 2} \rbrack\end{matrix}$

In Equation 2 above, P_(CMAX,c)(i) denotes maximum transmit powerassigned to the UE at the subframe i of the serving cell c, and isdetermined by the UE on the basis of a parameter received from the BS ora UE-specific parameter.

Δ_(F) _(—) _(PUCCH)(F) is provided by a higher layer, and a value ofΔ_(F) _(—) _(PUCCH)(F) corresponds to a PUCCH format F. Δ_(T×D)(F′)denotes a value given by a higher layer when the UE is configured by thehigher layer to transmit a PUCCH at two antenna ports.

P_(O) _(—) _(PUCCH) denotes a value given by the higher layer, and g(i)denotes a current PUCCH power control regulation state. PL_(c) denotes avalue regarding a path loss.

h(n_(CQI), n_(HARQ), n_(SR)) is a value depending on the PUCCH format,where n_(CQI) corresponds to the number of CQI information bits andn_(SR) is either 1 or 0 when SR is set in the subframe i. n_(HARQ)denotes the number of HARQ bits transmitted in the subframe i when oneserving sell is assigned to the UE. When multiple serving cells areassigned to the UE, n_(HARQ) is the number of transport blocks receivedin a subframe (i−k_(m)) or (the number of transport blocks received inthe subframe (i−k_(m))+1 (if an SPS release PDCCH is not received in thesubframe (i−k_(m))). In FDD, k_(m)=4.

With respect to the PUCCH format 3, h(n_(CQI), n_(HARQ), n_(SR)) isgiven by Equation 3 below.

$\begin{matrix}{{h( {n_{CQI},n_{HARQ},n_{SR}} )} = \frac{n_{HARQ} + n_{SR} - 1}{2}} & \lbrack {{Equation}\mspace{14mu} 3} \rbrack\end{matrix}$

Referring to Equation 3 above, when ACK/NACK is transmitted by beingjointly coupled to different UCI (e.g., SR), the PUCCH transmit powerP_(PUCCH) can be determined by treating the different UCI as if it isACK/NACK. That is, an information bit of the SR is treated as if it isan information bit of the ACK/NACK.

A method of multiplexing UCI information (i.e., CQI, ACK/NACK, SR) in acarrier aggregation system has been described in the present inventionwhen there is no PUSCH transmission. The UCI multiplexing method can becommonly applied to all UEs in a cell, or can be applied to some UEshaving insufficient uplink transmit power. In addition, theaforementioned methods may be configurable according to a choice of theBS.

FIG. 22 is a block diagram showing a BS and a UE according to anembodiment of the present invention.

A BS 100 includes a processor 110, a memory 120, and a radio frequency(RF) unit 130. The processor 110 implements the proposed functions,procedures, and/or methods. Layers of a radio interface protocol can beimplemented by the processor 110. The memory 120 coupled to theprocessor 110 stores a variety of information for driving the processor110. The RF unit 130 coupled to the processor 110 transmits and/orreceives a radio signal.

A UE 200 includes a processor 210, a memory 220, and an RF unit 230. Theprocessor 210 implements the proposed functions, procedures, and/ormethods. Layers of a radio interface protocol can be implemented by theprocessor 210. The processor 210 performs channel coding on informationbits of UCI to generate encoding information bits, modulates thegenerated encoding information bits to generate complex-valuedmodulation symbols, and performs block-wise spreading on thecomplex-valued modulation symbols to multiple SC-FDMA symbols on thebasis of an orthogonal sequence. In addition, the processor 210determines transmit power for a physical uplink control channel thattransmits the complex-valued modulation symbols to the BS 100 on thebasis of an information bit of first UCI and an information bit ofsecond UCI included in the information bits of the UCI. The memory 220coupled to the processor 210 stores a variety of information for drivingthe processor 210. The RF unit 230 coupled to the processor 210transmits and/or receives a radio signal. Further, the RF unit 230transmits the spread complex-valued modulation symbols to the BS.

The processors 110 and 210 may include an application-specificintegrated circuit (ASIC), a separate chipset, a logic circuit, a dataprocessing unit, and/or a converter for mutually converting a basebandsignal and a radio signal. The memories 120 and 220 may include aread-only memory (ROM), a random access memory (RAM), a flash memory, amemory card, a storage medium, and/or other equivalent storage devices.The RF units 130 and 230 may include baseband circuit for processing aradio signal. When the embodiment of the present invention isimplemented in software, the aforementioned methods can be implementedwith a module (i.e., process, function, etc.) for performing theaforementioned functions. The module may be stored in the memories 120and 220 and may be performed by the processors 110 and 120. The memories120 and 220 may be located inside or outside the processors 110 and 210,and may be coupled to the processors 110 and 210 by using variouswell-known means. Although the aforementioned exemplary system has beendescribed on the basis of a flowchart in which steps or blocks arelisted in sequence, the steps of the present invention are not limitedto a certain order. Therefore, a certain step may be performed in adifferent step or in a different order or concurrently with respect tothat described above. Further, it will be understood by those ordinaryskilled in the art that the steps of the flowcharts are not exclusive.Rather, another step may be included therein or one or more steps may bedeleted within the scope of the present invention.

Various modifications may be made in the aforementioned embodiments.Although all possible combinations of the various modifications of theembodiments cannot be described, those ordinary skilled in that art willunderstand possibility of other combinations. For example, thoseordinary skilled in the art will be able to implement the invention bycombining respective structures described in the aforementionedembodiments. Therefore, the present invention is not intended to belimited to the embodiments shown herein but is to be accorded the widestscope consistent with the principles and novel features disclosedherein.

1. A method for transmitting uplink control information (UCI), performedby a user equipment, in a wireless communication system, the methodcomprising: generating encoded information bits by performing channelcoding on information bits of the UCI; generating a modulation symbolsequence by modulating the encoded information bits; generating a spreadsequence by block-wise spreading on the modulation symbol sequences withan orthogonal sequence; and transmitting the spread sequence to a basestation through an uplink control channel, wherein the information bitsof the UCI comprises a first UCI bit sequence and a second UCIinformation bit.
 2. The method of claim 1, wherein the spread sequenceincludes a sequence generated by multiplying some modulation symbols ofthe modulation symbol sequence by an element of the orthogonal sequence.3. The method of claim 2, wherein the number of some modulation symbolsis equal to the number of subcarriers included in a resource block. 4.The method of claim 1, wherein transmission power of the uplink controlchannel is determined based on the number of bits of the first UCI bitsequence and the second UCI information bit.
 5. The method of claim 1,wherein the first UCI bit sequence is anacknowledgement/non-acknowledgement (ACK/NACK) bit-stream concatenatedwith an acknowledgement/non-acknowledgement (ACK/NACK) information bitsfor each of serving cells, and the second UCI information bit is ascheduling request (SR) information bit.
 6. The method of claim 5,wherein the SR information bit is appended to the end of the ACK/NACKbit-stream.
 7. The method of claim 6, wherein the SR information bit isone bit.
 8. The method of claim 1, wherein the spread sequence istransmitted to the base station through 1^(st), 3^(rd), 4^(th), 5^(th),and 7^(th) single carrier-frequency division multiple access (SC-FDMA)symbols in a slot consisting of 7 SC-FDMA symbols.
 9. The method ofclaim 8, wherein a reference signal is transmitted in 2^(nd) and 6^(th)SC-FDMA symbols in the slot.
 10. The method of claim 1, wherein thespread sequence is transmitted via a primary cell in which the userequipment performs an initial connection establishment procedure or aconnection re-establishment procedure with respect to the base station.11. The method of claim 1, wherein the modulation symbol sequence isgenerated by performing quadrature phase shift keying (QPSK) on theencoded information bits.
 12. An apparatus for transmitting uplinkcontrol information, the apparatus comprising: a radio frequency (RF)unit for transmitting or receiving a radio signal; and a processorcoupled to the RF unit, wherein the processor is configured for:generating encoded information bits by performing channel coding oninformation bits of the UCI; generating a modulation symbol sequence bymodulating the encoded information bits; generating a spread sequence byblock-wise spreading on the modulation symbol sequences with anorthogonal sequence; and transmitting the spread sequence to a basestation through an uplink control channel, wherein the information bitsof the UCI comprises a first UCI bit sequence and a second UCIinformation bit.
 13. The apparatus of claim 12, wherein the first UCIbit sequence is an acknowledgement/non-acknowledgement (ACK/NACK)bit-stream concatenated with an acknowledgement/non-acknowledgement(ACK/NACK) information bits for each of serving cells, and the secondUCI information bit is a scheduling request (SR) information bit. 14.The apparatus of claim 13, wherein the SR information bit is one bit,and is appended to the end of the ACK/NACK bit-stream.
 15. The apparatusof claim 12, wherein transmission power of the uplink control channel isdetermined based on the number of bits of the first UCI bit sequence andthe second UCI information bit.